Glaciers are vast, stationary sheets of solid ice that cover an expanse. When these massive frozen sheets of water move over rock formations, they erode it away as they go.
Erosion creates landforms such as eskers, drumlins and kettle lakes as it leaves behind alluvial deposits of sand and gravel that form landforms like eskers, drumlins and kettle lakes.
Which term best characterizes glacial erosion?
Plucking
Glaciers move rocks and sediment across land surfaces, eroding as they go. At the same time, however, they deposit sediment that alters landscape features as it accumulates; ultimately creating many of today’s landforms.
Plucking occurs when water seeping up from beneath a glacier seeps around lumps of broken and cracked rock, weakening their bond to their host bedrock, thus lifting them from it and plucked them free from being attached by this bedrock.
Abrasion refers to the process by which glaciers use ice as sandpaper to scrape rock fragments into dust, creating scratches known as striations on its surface. Abrasion also contributes to broad U-shaped valleys which fill with water over time to form Great Lakes in North America and Europe.
Glacier sediment can often be poorly sorted, consisting of various rock fragments of different sizes clumped together together into till, which is non-sorted glacial drift consisting of both large pieces (such as rocks) and fine material ranging from sand to clay particles.
Abrasion
Glacier ice scrapes against bedrock beneath it, creating what’s known as abrasion – which results in some of the most distinctive landforms associated with glacial erosion, such as moraines, U-shaped valleys, cirques and rock basins. Abrasion occurs on decametric to hectometric scales and is much more effective than fluvial erosion processes.
Glacial erosion can create glacial striations scars on bedrock surfaces that are distinctive, marking that an area has previously been covered by glaciers – these scars being particularly prevalent in alpine cirques.
Freeze-thaw weathering
Freeze-thaw weathering is an extremely powerful glacial erosion process. When water seeps into cracks in rocks and freezes overnight, expanding and widening them, more water seeps in and the cycle continues; eventually weakening them over time until large rocks break apart into smaller fragments or crevices form to provide unique environments that support unique forms of life such as plants or fauna that thrive there.
Climate is expected to have an influence on erosion rates since sliding is dictated by thermal regime of glaciers; however, empirical evidence of such influence remains limited20. This may be because erosion rate data cover broad geographical areas rather than individual years and can contain large uncertainties due to compilation over broad geographic areas that often represent short climate periods rather than individual ones; particularly for glaciers with steep profiles where response to climate can be determined primarily by bedrock slope.
Moraine
Moraines are large deposits of boulders, pebbles, sand and dirt deposited alongside glaciers as a result of plowing by glaciers as they move forward, collecting rocks and debris that it later deposits when it stops or melts away. Moraines may form ridges, basins or other landforms and typically reach kilometric scale.
Glacial erosion by abrasion involves the scraping action of rocks carried by glaciers as they cut into and scour through bedrock and valley walls, producing distinctive landforms such as striations, grooves and glacial polish. It also accounts for many glacial landscape features like cirques, troughs and rock basins being unbalanced topographically. Larger forms such as roches moutonnees and rock drumlins range in size from decametric to kilometric; smaller moraines come under various names including ground terminal or lateral moraines depending on where they appear on glacial surfaces; typically terminal moraines appear at either ends of glacial surfaces.